1. Field of the Invention
The present invention relates to a keyboard device suitable for use in, for example, a notebook personal computer which needs to be thin. In addition, the present invention relates to a personal computer employing the aforementioned keyboard device.
2. Description of the Related Art
One type of personal computer includes a rotatable cover above the computer body. A keyboard device is incorporated in the computer body, and a display device is incorporated in the rotatable cover. When the personal computer is in use, the cover with a display device incorporated therein is opened, whereas when the personal computer is not in use, the cover is closed so that the keyboard device is covered from above it. In the personal computer of the type described above, in order to make the keyboard device thinner, the key switches of the keyboard device are formed, as shown in FIGS. 10 and 11.
Each key switch has a boat-shaped key top 58, two retainer portions 58 disposed at the back side of each key top 58, two retainer portions 58c each with a slide groove 58b, and a key top supporting structure L disposed below each key top 58. Each key top supporting structure L comprises a first lever portion 56 and a second lever portion 57, with the first lever portion and the second lever portion being combined so as to form a cross. One end of each first lever portion 56 is rotatably retained by the retainer portions 58a of the key top 58 associated thereto. One end of each second lever portion 57 is slidably inserted into the slide grooves 58b in the retainer portions 58c of the key top 58 associated thereto.
Below the key top supporting structures L is disposed a key top supporting member 55 with a slide groove 55b for slidably retaining the other end of the first lever portions 56, and a retainer portion 55a for rotatably retaining the other end of the second lever portions.
A membrane switch 54 is disposed below the key top supporting member 55 so as to be slidable on a flat supporting substrate 60 and between the key top supporting member 55 and the supporting substrate 60. The membrane switch 54 is a laminated structure including, from bottom to top, a protective sheet 54a, a stationary contact sheet 54b, a spacer sheet 54c, a movable contact sheet 54d, and a protective sheet 54e. These sheets are integrally bonded together. At a hole 54f in the spacer sheet 54c, a contact 54g on the sheet 54d and a contact 54h on the sheet 54d oppose each other.
A dome-shaped resilient member 59 with a protrusion 59a used for operating a switch is provided below each key top supporting structure L, such that the top portion thereof opposes its associated key top supporting structure L and the bottom portion is mounted to the membrane sheet 54.
Accordingly, the keyboard device is constructed as described above.
As shown in FIGS. 12 and 13, the personal computer includes a cam projection 515a and a spring member 517. The cam projection 515a is provided at the front side of the cover 515 with a display device (not shown). The spring member 517 is disposed between the membrane switch 54 of the keyboard device mounted within a body 513 and a side wall 516 of the body 513.
In addition, when the personal computer having the above-described structure is ordinarily used by opening the cover 515 and operating the keyboard device 512, the key top supporting structures L are raised and supported by their corresponding resilient members 59 at their highest positions, as shown in FIG. 10. When an operator pushes a dome-shaped key top 58 downward against the resilient force of the resilient member 59 associated thereto, the inwardly projecting portion 59a of the associated resilient member 59 pushes the protective sheet 54e and the sheet 54d of the membrane switch 54, causing the contact 54h to come into contact with the contact 54g, whereby the switch is set in an on state.
Thereafter, releasing the key top 58 causes the resilient member 59 to return back to its original state due to its resiliency, and the associated supporting structure L and key top 58 to be restored back to its original state, causing the contact 54h to separate from the contact 54g, whereby the switch is set in an off state.
Accordingly, contact switching is performed.
As shown in FIGS. 11 and 13, lowering the cover 515 onto the keyboard device 512 causes the cam projection 515a to engage the left end of the membrane switch 54 of the keyboard device, causing the membrane switch 54 to move to the right against the spring force of the spring member 517. This causes the membrane switch 54 to slide in sliding contact between the supporting substrate 60 and the key top supporting member 55, and the resilient members 59 to move in the same direction and move out from below their corresponding key top supporting structures L. Disengagement of the resilient members 59 from below their corresponding key top supporting structure L causes the key top supporting structures L to be lowered due to its own weight, causing the key tops 58 to be lowered downward. This reduces the thickness of the entire keyboard device 512.
When the cover 515 is opened, the cam projection 515a disengages the membrane switch 54, whereby the spring member 517 causes the membrane switch 54 to slide in sliding contact between the supporting substrate 60 and the key top supporting member 55, and move back to its original position. Since, as a result of the sliding movement of the membrane switch 54, the resilient members 59 slide back to the bottom portion of their corresponding key top supporting structures L in sliding contact therewith, the key top supporting structures L are pushed back upward by their respective resilient members 59, which in turn causes the corresponding key tops 58 to rise upward and horizontally in order to be supported at their highest positions.
Thereafter, operations, such as those described above, are repeated to perform contact switching.
In such conventional keyboard devices and personal computers employing the aforementioned conventional keyboard devices, since the membrane switch 54 is slid, the electrical connecting structure between the electrical circuit in the personal computer and the sliding membrane switch 54 is complicated, which not only leads to high costs but also to lack of electrical reliability.
In addition, since the resilient member 59 is slid along its associated key top supporting structure L, the resilient member 59 has a shorter life. Moreover, since the resilient member cannot move smoothly, it cannot be operated with ease.